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A Diamondbacks’ Perspective on The Trade Deadline

Opportunity knocks!

Remember when the Dodgers beat the Diamondbacks in 2017? This season is different!
Remember when the Dodgers beat the Diamondbacks in 2017? This season is different!
Photo by Sarah Sachs/Arizona Diamondbacks/Getty Images

As of 17 June, the Diamondbacks had a 65% chance of reaching the playoffs per Opportunity knocks! An acquisition could improve their odds, and improve the odds of advancing beyond the first round.

At the trade deadline, what would be the best position to acquire?

To get the most improvement from an acquisition, an idea is to improve the weakest position. Wins Above Average (WAA) is ranked for all positions at Baseball Reference.

  • WAA at Second base (think Ketel Marte) ranked second best in the Majors. No improvement needed at second base.
  • The Diamondbacks have some young and talented outfielders – the outfield in general ranked sixth best WAA in the Majors. No improvement needed in the outfield.
  • Every position’s WAA ranked eighth best or better except pitching.

Let’s look at starting pitching.

Four statistics that compare the Diamondbacks’ starting pitching to the other teams (wOBA from Baseball Savant and the other stats from FanGraphs):

  • 4.5 xFIP ranked 23rd best.
  • 4.4 FIP ranked 16th best.
  • 4.67 ERA ranked 21st best.
  • .333 wOBA ranked 23rd best.

There is room for improvement. Acquiring a starting pitcher could improve their wins in two ways:

An acquired starting pitcher allows very few runs. Ideally, he pitches 6 innings and allows zero runs, per Mike Hazen’s comment:

“We’ve been playing very dramatic baseball lately. We either win it or lose it in the ninth inning, and that’s not a great way for a baseball team to go through life. We’d like it to be 6-0 in the seventh inning and then just ease on through the last six or nine outs of the game.” — Mike Hazen, June 2023

This season in the Majors, the average ERA is 4.28. When acquisition candidates are evaluated, one criteria should be that their ERA is lower than 4.28. One caveat is that if their FIP and xFIP are much better than their ERA, then that the candidate deserves special consideration.

An acquired starting pitcher stays deep into each game, thereby reducing the bullpen’s workload to keep them fresh and at their best.

The Diamondbacks’ starting pitchers faced 42.9% as many batters in the sixth inning as they faced in the first inning (a rough approximation of how many times starting pitchers made it through the sixth inning). The Diamondbacks rank the 19th most in the Majors.

The following table shows that rough approximation for the individual Diamondbacks. It shows that the top five are 25.8% or higher.

2023 season, games through 16 June. Data from Baseball Savant.

My view is that when acquisition candidates are evaluated, one criteria should be that they complete the sixth inning in at least 50% of their starts. That would rank them high in the above table.

Two series show benefits of acquiring a starting pitcher.

In June, the Diamondbacks played the Braves and the Phillies. These are two great teams who were playing excellent baseball. In the playoffs, this level of competition is what the Diamondbacks can expect.

In those two series, the Diamondbacks lost five games. In those lost games Zac Gallen and Merrill Kelly pitched only once each. Because Gallen and Kelly were mostly absent, these series are an opportunity to see the potential impact of an acquisition. Let’s look at the reasons for the losses to see the potential impact of adding a starting pitcher.

Did bullpen workload matter? Looking at the number of bullpen pitches on game day plus the previous two days (hat tip to samath for his official AZ Snake Pit table with bullpen pitches) shows that the bullpen was rested for the Braves series (3-day pitches ranged 104 to 151) and it was frazzled for the Phillies series (3-day pitches ranged 200 to 246). The bullpen results were 2.33 runs per game when rested in Braves series and 3.25 runs per game when frazzled in Phillies series. My conclusion is that if a starter acquisition rests the bullpen, it could be worth nearly one run per game! That’s huge! Even half a run per game would be awesome!

Does the starter’s runs allowed matter?

Braves Series. The Diamondbacks were outscored while the Diamondbacks bullpen pitched (1 run vs 7 runs). The only Diamondback win was when the Merrill Kelly held the Braves to 2 runs in 7 innings, and the bullpen held the Braves scoreless. So despite the rested bullpen, when Diamondbacks were outscored late in the games it mattered. A starting pitcher acquisition can’t change that situation.

Phillies Series. In three games the Diamondbacks’ starters left the game with the Phillies ahead. In one game, the starter left with the game tied. Although the Diamondbacks scored 10 runs while the Diamondbacks bullpen pitched, it was only enough to win one game by one run. My conclusion is that it would be better if the starting pitchers left the game with the lead. A starting pitcher acquisition who allows less runs could help win games.

How good would the acquired starting pitcher’s FIP and expected FIP need to be?

FIP and xFIP are good stats to consider because they are independent of fielding.

For this season, the following table shows these stats for some of the Diamondbacks starters.

2023 Season, games through 16 June. Data from FanGraphs.

After the core (Gallen/Kelly/Davies), the next starter has a 4.72 FIP and a 5.15 xFIP (Ryne Nelson). My view is that when acquisition candidates are evaluated, one criteria should be that their FIP and xFIP are significantly better than Ryne Nelson’s. My strong preference would be FIP and xFIP better than 4.28 (the average ERA in the Majors).


The best Diamondbacks’ acquisition would be a starting pitcher because that is their weakest position compared to other teams. The acquired starting pitcher will add wins in two ways - allow less runs and keep the bullpen fresh and at their best. An ideal acquisition completes the sixth inning in at least half his starts, with an ERA/FIP/xFIP of better than 4.28.